An additional five years of “containement” would be added when the sentence is due to expire.

That can be repeated at the end of each five years. However, it is also an ongoing assessment, meaning the offender can be released at any point where the authorities believe they no longer pose a risk.

Norwegian Prime Minister Jens Stoltenberg said the atrocity is the worst crime since the Second World War and signalled in its immediate aftermath that the country’s penal system may have to be examined.